Scott Silva wrote:
I'm curious as to why 2 complete dd'd copies don't pair at boot.
One comes up running and it does work to mdadm --add the partner
partitions and after the resync they do automatically pair at boot.
Are they dd copies of the different nodes (IE.. dd copy of sda
paired with dd copy of sdb)?
No - what was sda was dd'd twice with the dups put in sda and sdb.
That is why it didn't work. The superblock knows which drive it was
on, and knows if there are dupes.
But I thought the locations were re-detected at boot/assembly time.
The other question is whether it is possible to change the uuid while
the system is running or if it would have to be done from a CD boot.
I've cloned several machines from one initial setup and if copies of
the disks ever find their way back into one box I'd prefer not to have
the wrong set try to re-sync.
The locations can re-detect, but I still think it will stop if it
detects 2 identical superblocks.
I don't think you can change the UUID of a running array, and I'm not
sure if you can do it easily on a stopped array. I think the safest
thing is to use the --add to join the pair. Since they are dd clones,
the sync should be fairly fast. Just be careful.
Yes, the sync does work fine and once finished the set will always start
itself.
I know that it seems like an easy way to clone machines, but I think
there are better and safer ways to clone machines.
You can't beat dd for getting everything exactly the same regardless of
what you changed - or just splitting the mirrors and letting each sync
to new partners but then you have to reinstall grub. I prefer
clonezilla for non-raid configurations but most of the machines I care
about are configured with raid1.
--
Les Mikesell
lesmikesell@xxxxxxxxx
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